darry wrote on 2024-05-22, 06:28:
According to that product page, this thing has 4 serial ports and 2 parallel ones. No drivers required.
Thanks for the extra research. I somehow missed the fact that the 16c552 also includes a parallel port. This changes my claim about the connections: The two internal connectors are likely the two parallel ports, and all four(!) serial ports are connected using the 37-pin connector on the slot bracket.
Trashbytes wrote on 2024-05-22, 05:17:out of curiosity would such a card have been used for external storage ?
That's quite unlikely. The data rate of a single serial port is 11kB/s in the best case, which is too low for storage applications. While all four serial ports in parallel yield up to 45kB/s, using four separate UARTs to connect to a single target is not how you would design a higher-bandwidth interface at that time (but now we have PCI Express with multiple lanes...). The only ports that might be used for interfacing with storage are the parallel ports, but you wouldn't put four useless serial ports onto a card if the card is only meant to interface to some storage unit using a parallel port.
The main purpose of this card indeed seems to be to interface to multiple external devices. The suggestions in this thread that this card might be used for a multi-line BBS or interfacing multiple industrial control units or lab equipment to automate manufacturing or measuring processes sound reasonable.